To the Editor After successful weight loss with weekly group sessions over the initial 6 months of the IDEA trial, individuals randomized to an enhanced intervention group using a physical activity tracking device regained more weight over the subsequent 18 months compared with participants randomized to a standard intervention not including use of this device.1 The results seem counterintuitive and remain insufficiently explained. We have a few questions that may lead to better understanding of the IDEA trial results.

First, what was the accuracy of the wearable technology system used in this trial? To provide valuable feedback to users, device accuracy is fundamental, and it was not reported whether the investigators evaluated accuracy of this device. If the device were to inform users that they were achieving greater physical activity than they truly were, this could have had a negative effect. Studies of physical activity trackers2 and other digital applications3reinforce the need for accuracy validation in digital health research.

Second, were participants surveyed regarding use of wearable devices other than the device provided? Wearables have been widely adopted by consumers, particularly among the demographic group in this trial. This poses a unique challenge in contrast to a pharmaceutical trial wherein the study drug is only available through the trial. Other available wearables appear to have competitive advantages over the wearable device used in the study, as it was discontinued despite a rapidly expanding $14 billion wearables market.4 The IDEA trial usability surveys indicated the device’s disadvantages. Approximately half of participants did not agree nor strongly agree that the device (worn on the upper arm) was comfortable. The device was typically worn only 4 hours per day. It remains possible that the trial actually tested use of a device, selected by the study team, with an unsatisfactory user experience against use of other devices, selected and self-initiated by participants, with superior user experiences.

Third, was usability of the website for the standard intervention group compared against that of the website for the enhanced intervention group? If the standard intervention group’s website provided a better user experience for monitoring eating and physical activity behavior, this may partly explain why the standard intervention group regained less weight. Still, given there was no true control group, it is unclear what effect any of these interventions had over no intervention.